We are examining the relationship between platelet adenine nucleotide metabolism and platelet function. The main thrust of our research is to determine how platelet adenine nucleotides participate in platelet aggregation. We are presently looking at three areas: (1) The adenine nucleotide response of ADP-induced aggregation. (2) The adenine nucleotide response of the collagen induced reaction. (3) The interaction between items 1 and 2. This latter aspect will be the focus of our attention. We plan to quantitate the stimulation of energy utilization by each of these agents and then determine whether, when combined, they have a synergistic reaction. Particular attention will be paid to the role of various agents which inhibit either reaction 1 or reaction 2, in that we will examine their effect in the interaction between collagen and ADP in our combined study.